In 1980 FIAT introduced a Bosch multiport fuel injection system in its vehicles. Introduced first on California-bound vehicles and, by 1981, on all U.S. vehicles, the Bosch system improved the performance, efficiency, reliability, and quality of engine operations. Solely responsible for a 23 horsepower increase on the 2 liter engines, this system, known as Bosch L-Jetronic, was popular not only on FIATs but on nearly every European car produced in the 1980’s.

The L-Jetronic was the first mass-produced, fully electronic fuel injection system. Prior to L-Jetronic, mechanical fuel injection systems had proven that directly injecting atomized fuel into the cylinder resulted in better engine operation. Combining this direct injection theory with electronic sensors, valves, and meters - all controlled by a central computer - resulted in better operation than before.

The basic operation is straightforward. An engine is basically an air pump, drawing mixed fuel and air into the intake manifold, compressing it (followed by a spark-triggered explosion), and expelling it through the exhaust manifold. In a fuel injection system the entire operation is based on the amount of air entering the system. The engine pulls air through an air filter and into an air flow meter. The air flow meter measures the amount of air entering the system. Once measured, the air flows into a large hose that is connected to the intake manifold (a plenum). The intake manifold has a throttle plate that is connected to the driver’s foot (the accelerator pedal). The position of this plate determines how much air is drawn into the manifold. Air is then passed into one of four barrels connecting the manifold to the cylinder head. A fuel injector is positioned each barrel and, as air passes through, fuel is sprayed for a specific amount of time into the air stream.

Download pdf Bosch L-Jetronic Fuel Injection Guide FIAT Fuel Injected Engines